Method of making an annular assembly of magnets for use as the field of a dynamoelectric machine

ABSTRACT

A method of assembling a plurality of arcuate magnets inside an annular member wherein said magnets are biased towards each other by a resilient member. A plurality of arcuate ceramic magnets are arranged in a generally end face to end face, spaced relationship to form an annular ring, and a compressible resilient spacer or spring member is placed between two magnets to hold them in assembly with a temporary shipping band or with the rotor part in which they are finally installed. In making the assembly, a deformable insert may also be placed between two adjacent magnets and then deformed to enlarge the gap in which it is received, thereby compressing the spring member. If the magnets are first formed into a preassembly with a shipping band for later assembly with a rotor part, and if a deformable insert is used to control the compression of the spring member, the deformable insert in forming the preassembly is preferably deformed only to a degree sufficient to hold the preassembly in assembly with only a degree of tightness sufficient to withstand normal handling, and after the magnets are inserted in the final rotor part and the shipping band removed, the deformable insert is deformed to a further extent to hold the magnets in assembly with the rotor part with a greater degree of tightness.

United States Patent 1 Phelon METHOD OF MAKING AN ANNULAR ASSEMBLY OFMAGNETS FOR USE AS THE FIELD OF A DYNAMOELECTRIC MACHINE [75] Inventor:Russell E. Phelon, Rio Piedras, RR.

[73] Assignee: R. E. Phelon Company, Inc., East Longmeadow, Mass.

[22] Filed: Jan. 6, 1972 [21] App1.No.: 215,828

Related (1.8. Application Data [62] Division of Ser. No. 60,296, Aug. 3,1970, Pat. No.

[4 11 Apr. 17, 1973 Primary Examiner-Charles W. Lanham AssistantExaminerCarl E. Hall Attorney-Donald K. Huber [57] ABSTRACT A method ofassembling a plurality of arcuate magnets inside an annular memberwherein said magnets are biased towards each other by a resilientmember.

A plurality of arcuate ceramic magnets are arranged in a generally endface to end face, spaced relationship to form an annular ring, and acompressible resilient spacer or spring member is placed between twomagnets to hold them in assembly with a temporary shipping band or withthe rotor part in which they are finally installed. In making theassembly, a deformable insert may also be placed between two adjacentmagnets and then deformed to enlarge the gap in which it is received,thereby compressing the spring member. If the magnets are first formedinto a preassembly with a shipping band for later assembly with a rotorpart, and if a deformable insert is used to control the compression ofthe spring member, the deformable insert in forming the preassembly ispreferably deformed only to a degree sufficient to hold the preassemblyin assembly with only a degree of tightness sufficient to withstandnormal handling, and after the magnets are inserted in the final rotorpart and the shipping band removed, the deformable insert is deformed toa further extent to hold the magnets in assembly with the rotor partwith a greater degree of tightness.

11 Claims, 30 Drawing Figures PAIENIED APR) '1 m5 SHEET 1 OF 5 FIG.2

PATENTEDAPR 1 H915 SHEET 3 [IF 6 Fla-lo METHOD OF MAKING AN ANNULARASSEMBLY OF MAGNETS FOR USE AS THE FIELD OF A DYNAMOELECTRIC MACHINECROSS-REFERENCE TO RELATED APPLICATION This application is a division ofcopending application Ser. No. 60,296, filed Aug. 3, 1970 now U.S. Pat.No. 3,63,050, issued May 16, 1972.

BACKGROUND OF THE INVENTION Thisinvention relates to dynamoelectricmachines using permanently magnetized material for establishing amagnetic field, and deals more particularly with the method of making anannular assembly of magnets to be used as such a field, such methodincluding the installation of the magnets in and the securement of themto a flywheel or other annular carrier.

In its broader aspects, the method of this invention may be used withvarious different types of dynamoelectric machines, such as motors orgenerators, using permanent magnet material for establishing a magneticfield, and may be used with such machines wherein the magnetic fieldmeans is either a rotating part or a stationary part. At present,however, the invention finds particular utility in application toelectric alternators for use with internal combustion engines whereinthe magnetic field means consists of a magnet ring installed in theflywheel of the engine for cooperation with a stator located within theflywheel. Accordingly, in the description which follows, and in thedrawings forming a part hereof, the invention is described in connectionwith various different constructions of flywheel alternators, but itshould be understood that the invention is not in its broader aspectsnecessarily limited to this application.

The general use of an annular magnet assembly in combination with aflywheel or other annular carrier is well known in the prior art. U.S.Pat. No. 3,132,270, for example, discloses a rotor annulus constructionfor use in an alternator. That annulus includes a series of magnets andpole pieces which are first formed into a self'sustaining unit whichunit is then placed into a die cavity and material used in the flywheelis subsequently cast therearound. The magnets are tangentially chargedand the pole pieces are used to provide pole faces on the interiorsurface of the flywheel rim and to provide flux-conducting paths betweenthe pole faces and the magnets. In making the self-sustaining unit themagnets and the pole pieces are assembled inside of a surrounding bandand are then spread into tight engagement with the band by inserting awedge member or shim between a magnet and a pole piece.

Recently, it has become known to use ceramic permanent magnets invarious dynamoelectric machines. These are magnets made of a hardferrite, such as barium ferrite, strontium ferrite or lead ferrite.Because of their magnetic properties these magnets may be radiallycharged without requiring a great radial thickness and may themselvesprovide pole faces, thereby eliminating the need for associated poleshoes or pole pieces. In fact, it has been found that an improvedwave-shape of alternator output voltage is obtained when pole shoes arenot incorporated in the alternator construction. In such an alternator,the output voltage is more closely sinusoidal than in constructionsusing pole shoes. It is believed that this is because when using poleshoes, on a rotor for example, the entire flux of a permanent magnettends to flow through its associated shoe when such shoe becomes onlyslightly overlapped with a stator pole, thereby rapidly changing theflux at the initiation of the overlap and possibly producing undesiredvoltage spikes in the output waveform, whereas with ceramic magnetsproviding their own pole faces this does not occur since the ceramicmaterial has a high reluctance in a direction parallel to the plane ofthe pole face.

Besides improving the output voltage wave-shape the use of ceramicmagnets also enables a reduction in cost by eliminating the cost of poleshoes or pole pieces. Also, and as part of this invention, theindividual pieces of ceramic magnet material may be made of relativelylarge circumferential extent and charged to provide a number ofcircumferentially spaced magnetic poles on each such piece of magnetmaterial. This has the advantage of further reducing the cost of thecompleted magnet ring and of increasing its versatility. That is, it maybe charged to provide various different numbers of magnetic poles,thereby when used as a generator rotor enabling it to be used withstators having different numbers of stator poles and/or producingdifferent types of outputs, such as single-phase, two-phase orthree-phase outputs.

Ceramic permanent magnets have a tendency to crack or chip if stressedto too high a compressive force. One object of this invention is toprovide a magnet annulus method of assembly whereby the load imposed onthe magnets is controllable so as to assure the maintenance of such loadwell below that causing cracking or other failure of the magnets.

BRIEF DESCRIPTION OF THE DRAWINGS Details of this invention will appearin the following description and appended claims, reference being madeto the accompanying drawings forming a part of the specification whereinlike reference characters designate corresponding parts in the severalviews.

FIG. 1 is a view, taken on the line 1-1 of FIG. 2, showing a flywheelalternator using a magnet assembly made in accordance with thisinvention.

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1.

FIG. 3 is a perspective view of a magnet preassembly used in making therotor of FIG. 1.

FIG. 4 us a perspective view of a spring element used in the preassemblyof FIG. 3.

FIG. 5 is a fragmentary sectional. view of the magnet preassembly ofFIG. 3 positioned for insertion in a flywheel.

FIG. 6 is similar to FIG. 5 but shows the magnets of FIG. 5 afterinsertion into the flywheel.

FIG. 7 is a fragmentary view similar to FIG. 5 but showing a magnetpreassembly comprising another embodiment of this invention andincorporating an adhesive material.

FIG. 8 is a fragmentary sectional view of a magnet preassemblycomprising another embodiment of the invention and taken on the line 8-8of FIG. 9.

FIG. 9 is a fragmentary elevational view taken on the line 9-9 of FIG.8.

FIG. 10 is a plan view of the spring element shown in FIGS. 8 and 9.

FIG. 11 is a fragmentary sectional view of a magnet assembly comprisinganother embodiment of the invention and taken on the line l111 of FIG.12.

FIG. 12 is a fragmentary elevational view taken on the line 12-12 ofFIG. 11.

FIG. 13 is a fragmentary sectional view showing the magnets of FIG. 11positioned in a flywheel, a portion of the section being taken through aspring element on the line 1313 of FIG. 12.

FIG. 14 is a fragmentary sectional view of a magnet preassemblycomprising still another embodiment of this invention.

FIG. 15 is a plan view of the spring element of FIG. 14.

FIG. 16 is a fragmentary end elevational view of a flywheel and magnetassembly comprising another embodiment of this invention, part of theflywheel being shown broken away, to reveal the magnet assembly.

FIG. 17 is a fragmentary sectional view taken on the line l7-l7 of FIG.16.

FIG. 18 is an end elevational view of a magnet preassembly comprisingstill another embodiment of the invention, this view showing thepreassembly with the magnets in an initial untightened conditionrelative to the shipping band and in place on a tool for effecting thetightening.

FIG. 19 is a perspective view of one of the deformable inserts used inthe magnet preassembly of FIG. 18.

FIG. 20 is an end elevational view of the magnet preassembly of FIG. 18after tightening.

FIG. 21 is a view similar to FIG. 18 but shows a magnet preassemblycomprising still another embodiment of the invention.

FIG. 22 is a perspective view of one of the nondeformable inserts ofFIG. 21.

FIG. 23 is an end elevational view of a magnet preassembly comprisinganother embodiment of the invention.

FIG. 24 is a perspective view of one of the resilient inserts of FIG.23.

FIG. 25 is a fragmentary sectional view showing the magnet preassemblyof FIG. 23 positioned for insertion in a flywheel.

FIG. 26 is a fragmentary sectional view similar to FIG. 25 but showingthe magnets in place in the flywheel.

FIG. 27 is a perspective view showing the magnets of FIG. 18 in place ina flywheel.

FIG. 28 is a fragmentary sectional view taken on the line 2828 of FIG.27.

FIG. 29 is a perspective view showing a flywheel and a one-piece magnetassembly comprising still another embodiment ofthis invention.

FIG. 30 is a perspective view similar to FIG. 29 but showing anotherembodiment of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS Turning first to FIGS. 1 and 2,these figures illustrate a flywheel alternator, indicated generally at10, including a magnetic field means made in accordance with the presentinvention. The alternator 10 includes a stator l8 and a flywheel 15adapted for connection to the crankshaft or the like of an engine andhaving a retaining rim portion 15a within which is located the magneticfield means in the form of a magnet assembly comprised of an annulararrangement or series of arcuate permanent magnets 12, 12 and interposedspring elements 13, 13. The rim portion 15a is of magnetic material andprovides a magnetic path for connecting the magnets 12, 12. The arcuatemagnets 12, 12 are arranged generally in an end face to end face, circumferentially spaced relationship to form an annular ring havingcircumferentially extending gaps between adjacent magnets, and a springelement 13 is located in each of the gaps. The stator 18 comprises acore 18a made of a plurality of radially outwardly extending statorpoles 19, 19. A generating winding 20 is located on each of the statorpoles l9, 19.

The magnets 12, 12 are made of a high coercive force ceramic permanentmagnet material, such as barium ferrite, strontium ferrite or leadferrite, of the oriented type, and are magnetized to form their-magneticpoles after being placed in the flywheel rim 15a. Preferably, and inaccordance with one aspect of this invention, they are of such acircumferential length that more than one magnetic pole may be formed oneach of their radially inner faces for cooperation with the stator poles19, 19. As shown in FIG. 1, the stator 18 includes twelve poles 19, 19and the rotor includes six magnets 12, 12 each magnetized to provide twomagnetic poles on its inner face for a total of twelve poles for theentire rotor, the alternator 10 therefore being adapted to provide asingle-phase output. The magnets 12, 12 are radially charged ormagnetized so that each magnetic pole on the inner face of a magnet hasa corresponding pole of opposite magnetic polarity located radiallyoutwardly thereof on the outer face of the magnet. The magnetized zonesof the magnets are also so magnetized that the poles on the inner facesof the magnets are of alternate magnetic polarity in going around thecircle defined by such inner faces, and likewise the magnetic polesformed on the outer faces of the magnets are of similar alternatemagnetic polarity, the flywheel rim 15a being ofa magnetic material soas to form a low reluctance flux path for the flow of flux betweenadjacent ones of the magnetic poles on the outer faces of the magnets.

The same rotor as shown in FIG. 1, with its magnets similarly magnetizedto provide twelve rotor poles, could also be used with an eighteen polestator to pro vide a three-phase output. It could also be magnetized toprovide three magnetic poles on each magnet, for a total of eighteenrotor poles, and used with an eighteen pole stator for a single-phaseoutput, or with a twentyseven pole stator for a three-phase output.Therefore, the same physical construction of a rotor may be used withoutchange, except possibly for the magnetization of its magnets, withvarious different stators to provide various different types of outputs.

One feature of this invention is directed to the manner in which themagnets are assembled with the flywheel or other carrier to form arotor. More particularly, the method of assembly makes use of apreassembly of magnets, inserts and a surrounding band. The preassemblyused in making the rotor in the flywheel 15 of FIG. 1 is shown in FIG. 3and indicated generally at 11. It includes a plurality of permanentmagnets 12, 12 arranged in a generally end face to end face, spacedrelationship to form an annular ring having gaps as shown betweenadjacent magnets 12, 12. A spring member or insert 13 is disposed ineach of the gaps, and a circular band 14 surrounds the magnets. The band14 may be placed around the magnets 12 by using any suitable techniqueand holds the spring members 13, 13 in compressed condition so that theyforce the magnets apart and into tight engagement with the band.

Once the preassembly ll of FIG. 3 is formed, it becomes a relativelyrigid unit and may be handled relatively roughly without danger of itscoming apart. Therefore, the use of the preassembly 11 allows it to bemade at one location and to be shipped to another location for assemblywith the flywheel or other carrier. These two locations may be differentparts of the same factory or may be in the factories of differentmanufacturers located at widely spaced points in the country. FIG. 4shows one of the spring member inserts 13 prior to its incorporationinto the preassembly 11 of FIG. 3. It will be noted that it consists ofa length of generally tubular shaped material having a longitudinal slottherein forming two spaced edges which are moved toward one another asthe member is compressed by forces applied to opposite sides of themember in a direction tending to close the slot. As explained in moredetail hereinafter, by observing the spacing between the spaced edges ofthe insert 13 after the in serts are placed in the preassembly 11, thespring forces imposed on the magnets may be roughly estimated and may beused to control the maximum extent of such forces.

FIGS. 5 and 6 show the method in which the magnets of the preassembly 11are placed into the flywheel rim a. Referring to FIG. 5, the outer facesof the magnets l2, 12 of the preassembly 11 define a circle having adiameter only very slightly less than the internal diameter of the outeror free edge of the rim 150. Therefore, when assembling the magnets withthe rim 15a, the preassembly 11 may be placed as shown in FIG. 5, withthe magnets 12, 12 partially entered into the rim 15a and with the band14 resting on the outer edge of the rim. Thereafter, the magnets may bepushed inwardly relative to the rim 15a by forces applied simultaneouslyto all of the magnets causing the magnets to slide out of the band 14and into the rim into their final positions as shown in FIG. 6. As shownin FIGS. 2, 5 and 6, the rim 15a of the flywheel is machined orotherwise formed to provide an undercut lip 16 at its outer edge and toform an annular recess for the magnets 12, 12 which is of a slightlylarger diameter than the internal diameter of the rim at the region ofthe lip 16. Therefore, as the magnets I2, 12 are pushed to their finalposition and past the undercut lip 16 the spring members 13, 13 willexpand the diameter of the magnet ring by forcing the magnets apart fromone another causing them to move radially outwardly into the recess ofthe rim at which position the undercut lip 16 engages the magnets toprevent them from thereafter moving axially out of the rim, or upwardlyin FIG. 6. The band 14 is left behind as the magnets are pushed into theflywheel rim and forms no part of the finished rotor assembly.

In the rotor assembly of FIG. I, the pressure exerted by the springmembers l3, 13 against the magnets tends to hold the magnets in placerelative to the rim 15a, and the undercut lip 16 adds additionalrestraint against movement of the magnets axially of the rim. Ifdesired, still further restraint against displacement of the magnetsrelative to the rim may be provided by bonding the magnets directly tothe rim. FIG. 7 is similar to FIG. 5 but shows a magnet preassemblybeing assembled with the rotor rim 15a and which preassembly alsoincludes a layer 17 of adhesive interposed between the outer face ofeach magnet and the surrounding band 14. This adhesive material ispreferably an epoxy adhesive in a substantially dry state that isapplied to the outer face of each magnet prior to its assembly with thespring members 13, 13 and the band 14. After the adhesive coated magnetsof FIG. 7 are pushed to their final positions, similar to the positionsoccupied by the magnets 12, 12 of FIG. 6, the rotor assembly is heatedto set the adhesive epoxy material. The assembly is then cooled and theepoxy effects a bond between the magnets and the flywheel rim. Thebiasing force of the spring elements 13, 13 causes the magnets 12, 12 tobe pressed against the flywheel rim during the setting of the adhesivethereby attaining a tight bond therebetween. Once the adhesive materialis cured and the bonding between the magnets 12, 12 and the rim 15a isaffected, the spring elements l3, 13 may be removed if desired, but itis presently preferred to retain them in the finished rotor. An adhesivematerial suitable for use in this instance is sold under the tradenamePLASTILOCK 6L5-4 and comprises a hycar-phenolic base in a methyl ethylketone thinner.

An alternative method of bonding the magnets 12, 12 to the flywheel rim15a is to place the adhesive material on the inside of the rim 15a priorto the insertion of the magnets rather than on the back faces of themagnets. In addition, there is available in the art an epoxy adhesivetape which may be applied to either the magnets or the flywheel rim 15ainstead of applying the material in semi-liquid form by methods such asbrushing or spraying followed by drying.

In keeping with the invention, various different types of springelements or inserts may be used between the magnets 12, 12 in place ofthe tubular spring elements 13, 13 shown in FIG. 4. FIGS. 8 to 15 showthree other different types of spring elements which may be used. Inparticular, FIGS. 8, 9 and 10 show the use ofa spring element 21 betweeneach pair of adjacent magnets 12, 12. The spring element 21 is a bowedpiece of spring material and has side edges which are received ingrooves 23, 23 formed in the end faces of the adjacent magnets 12, 12.Each spring member 21 further includes lip members 22, 22 at itsopposite ends which extend laterally a short distance beyond the magnetengaging side edges and aid in retaining the elements 21, 21 axially inplace between the magnets 12, 12.

FIGS. 11, 12 and 13 show the use of an insert 24 between adjacentmagnets 12, 12 which insert 24 is ofa generally U-shaped cross-sectionhaving two end flanges which are received in grooves in the adjacentends of the magnets l2, 12. The rounded base of the insert 24 engagesthe band 14 in the preassembly, as shown in FIG. 11, and after themagnets and spring elements are inserted into the flywheel rim 15a, asshown in FIG. 13, the base of the spring element 24 resides under theundercut lip of the rim so that such lip 16 prevents the element frombeing axially displaced.

FIGS. 14 and 15 show the use of :a helical spring element 25 betweenadjacent magnets 12, 12 and received in conforming grooves in the endfaces of the magnets.

The helical spring element 25 is twisted by applying a torque atopposite ends with some mechanical means prior to and during itsinsertion between the end faces of the magnets 12, 12. This twistingprocess reduces its diameter and after insertion between the magnets 12,12, the twisting force is removed thereby allowing the helical springmember to expand diametrically toward its original diameter and to pressagainst the opposite end faces of the adjacent magnets 12, 12 so as totend to exert a spreading force thereon tightly pressing the magnetsagainst the surrounding band 14 of the preassembly and against the rim15a of the final assembly.

A magnet assembly generally similar, for example, to the preassembly llof FIG. 3 may also be used in association with a flywheel or othercarrier made of a non-magnetic material. In this instance, however, themagnet assembly must include some means to provide a low reluctance fluxpath between the magnetic poles on the outer faces of the magnets. FIGS.16 and 17 show a flywheel 15 made of non-magnetic material, particularlya die-cast material such as cast-aluminum or aluminum alloy. In thisflywheel, the magnets l2, l2 and the spring inserts 13, 13 are die-castin place. That is, they are embedded in the cast material of the rotorrim 27. In addition, a continuous ring 26 of magnetic material surroundsthe magnets 12, 12 and provides the low reluctance flux path between thealternate magnetic poles on the outer faces of the magnets, the ring 26also being cast in place in the rotor rim 27. The ring 26 of FIGS. 16and 17 is similar to the band 14 of the preassembly ll of FIG. 13 exceptfor being 'of a larger radial dimension and of an axial lengthsubstantially equal to the axial length of the magnets l2, 12 so as tooverlie the full extent of each outer face of each magnet and providethe low reluctance flux path. The ring 26 may therefore be used informing the magnets and spring elements into a preassembly. Thepreassembly is then placed in a suitable mold and the material of thecarrier cast around it to form the finished flywheel, the ring 26 inthis case remaining with the finished flywheel rather than being removedfrom the magnets during the final assembly. Of course, the preassemblyconsisting of the magnets 12, 12, inserts 13, 13 and ring 26 need notnecessarily be die-cast in place when used with a nonmagnetic rotormaterial and, if desired, may be otherwise fixed, as for example, byadhesive bonding, to a non-magnetic carrier.

As mentioned previously, the spring inserts placed between the end facesof adjacent magnets to spread the magnets and to hold them in tightassembly with the retaining band of the preassembly may be inserted inany suitable manner. However, some forms of preassemblics lendthemselves to a preferred method of assembly carried out in accordancewith steps involving a more detailed aspect ofthis invention andillustrated by FIGS. 18 to 24. Considering first FIG. 18, this figureshows a magnet preassembly in place on a tool 28 for tightening themagnets against the surrounding band 14. This preassembly is differentfrom the one shown in FIG. 3 in that it includes only one spring member13 placed in one of the gaps between the magnets 12, 12. The other gapsbetween the magnets 12, 12 are filled with deformable inserts 30, 30similar to the one shown in FIG. 19. That is, each deformable insert 30is a length of tube, of aluminum for example, having a generally ovalcross-section. The relative sizes of the band 14, the magnets 12, 12,the spring member 13 and the deformable inserts 30, 30 is such thatthese parts may be readily assembled around the tool 28 by hand with thespring member 13 and inserts 30, 30 being easily manually slipped intoplace between the magnet end faces. That is, in this initial assemblythe spring member 13 is not compressed.

The tool 28 includes a plurality of radially movable rams 29, 29 eachlocated adjacent the position of a respective one of the deformableinserts 30, 30, and after the initial assembly of all of the parts ofthe preassembly the rams 29, 29 are simultaneously moved radiallyoutwardly and into deforming engagement with the inserts 30, 30. Thatis, as the rams 29, 29 move radially outwardly, they tend to deform thedeformable inserts 30, 30 toward more circular shapes thereby enlargingthe gaps in which they are received and spreading the magnets to closethe gap containing the spring element 13, thereby compressing the springelement 13. After the deformable inserts 30, 30 are so deformed, therams 29, 29 are retracted and, thereafter, the compression of the springinsert 13 in cooperation with the now deformed inserts 30, 30 holds theparts of the preassembly in a relatively rigid assembled condition.

FIG. 20 shows the preassembly of FIG. 18 removed from the tool 28 andafter the deformable members 30, 30 have been deformed to the point thespring member 13 is compressed to an extent sufficient to hold theillustrated parts in assembly with one another. It should be noted thatthe magnets l2, 12 are subject to cracking or other failure if subjectedto too high compressive loads, and the method of assembly illustrated byFIG. 18 provides a method whereby the force imposed on the magnets maybe accurately controlled. More particularly, the deformation of thespring member insert 13 provides a gauge of the force imposed on themagnets and by deforming the deformable inserts 30, 30 to provide apredetermined final spacing between the edges of the spring insert 13, apredetermined biasing force may be obtained.

FIGS. 18 and 20 show a preassembly including only one spring element 13in combination with deformable elements placed in all other gaps of thepreassembly. This combination of spring inserts and deformable insertsis, however, not critical and, if desired, the number of spring insertsand deformable inserts may vary. In addition, one or more of thedeformable inserts 30, 30 may be replaced by non-deformable inserts and,of course, the exact construction of the deformable inserts may varyfrom the oval tubular ones shown, the important criterion being that thedeformable insert under the influence of radially outwardly directedpressure will deform so as to increase its dimension circumferentiallyof the preassembly so as to force apart the magnet end faces definingthe gap in which it is received.

By way of further example, FIG. 21 shows a magnet preassembly, in placeon another forming tool 34 consisting of magnets 12, 12, a surroundingband 14, one spring insert 13, one deformable insert 30 and fournon-deformable inserts 36, 36, such as shown in FIG. 22, consisting ofshort lengths of cylindrical stock. Since there is only one deformablemember 30, the tool 34 similarly includes only one radially movable ram38 for deforming the insert 30 to spread the end faces of the magnetsdefining the gap in which it is received and to thereby compress thespring 13 to thereafter hold the parts of the preassembly in anassembled condition.

FIG. 23 shows still another preassembly consisting of magnets 12, 12, asurrounding band 14, two spring inserts 40, 40, two non-deformableinserts 42, 42 and two deformable inserts 30, 30, this figure showingthe preassembly after the deformation of the inserts 30, 30 and theconsequent compression of the spring inserts 40, 40. In this case, thespring inserts 40, 40 are comprised of short lengths of rubber or otherelastorneric material having, prior to compression, a generallyrectangular cross-section as shown in FIG. 24.

In the previously illustrated rotors using a magnet assembly combinedwith a flywheel or other carrier of magnetic material, the magnets afterassembly with the carrier have been axially retained in place, not onlyby the frictional force exerted by the magnets against the inner surfaceof the carrier or flywheel rim, but by additional means such as theundercut lip 16 of FIG. 2, or the adhesive material 17 of FIG. 7. Suchauxiliary means for aiding in holding the magnets axially in place,however, have been found to be unnecessary in many applications. In someinstances the undercut lip may be eliminated and adhesive used to aid inretaining the magnets in place. This is illustrated by FIGS. 27 and 28which show the magnets of FIG. 18 held in place not only by the force ofthe spring element, but also by an adhesive layer 17 between each magnetand its flywheel rim a, the flywheel rim not, however, including anundercut lip.

In still some other instances the adhesive may also be eliminated andthe force of the spring element or elements alone used to retain themagnets in the final assembly. In fact, if the spring elements used tohold the magnets in place are properly designed and held in properlycompressed states in the finished assembly, extremely large forces maybe required to thereafter displace the magnets from the flywheel orother carrier into which they are placed. FIGS. and 26 show the assemblyofa magnet preassembly 11 with a flywheel in a situation wherein themagnets are to be held in place solely by the force exerted thereon byspring element or elements. The rotor rim 15a of FIGS. 25 and 26 issimilar to that shown in FIG. 2 except for not including any undercutlip. Therefore, as the magnets l2, 12 of the preassembly are moved fromthe position shown in FIG. 25 into the rim to the position shown in FIG.26, they do not substantially change in diameter and are merely broughtby such movement to the FIG. 26 position into permanent engagement withthe interior surface of the rotor rim 15a, In connection with thismethod of assembly, the preassembly II is preferably one including oneor more deformable members, such as the preassembly shown in FIGS. 18and 20, and in making the preassembly the deformable member or membersare deformed only to the extent necessary to slightly compress thespring member or members to create only a low degree of force holdingthe parts in assembly and sufficient only to resist disassembly bynormal handling and shipping loads. This, therefore, keeps to a minimumthe forces necessary to push the magnets from the FIG. 25 position tothe FIG. 26 position when inserting them into a flywheel or othercarrier. Then, after the magnets are in position in the flywheel orother carrier, the deformable member or members are further deformed, bya suitable tool such as the tool 28 of FIG. 18, to further compress thespring member or members and to thereby increase the forces holding themagnets in the carrier.

Also, as previously mentioned, one aspect of this invention is the factthat the magnets used in the rotor are made of a ceramic material andare so designed that when magnetized more than one magnetic pole may beformed on the inner face of each magnet. As a limiting situation, themagnet ring may be composed of a single annular one-piece magnet chargedto provide alternate poles on its inner face. Such a construction isshown in FIG. 29 wherein the magnet is shown to consist of a circularmember 46 made of ceramic permanent magnet material and inserted intothe rim 15a of the flywheel. The ring magnet 46 is held in place in theflywheel rim 15a by a layer of adhesive 48 and after insertion into theflywheel is magnetized to produce alternate magnetic poles on its innerface as shown.

It will also be appreciated'that in cases where the magnet ring is madefrom a plurality of magnets there need not in all instances be insertsplaced between each pair of adjacent magnet end faces. Instead, it ispossible to allow some pairs of adjacent end faces to abut one anotherwithout placing inserts therebetween. For example, FIG. 30 shows a rotorcontaining a magnet ring comprised of a plurality of magnets 12, 12wherein such magnets have end faces which abut one another at the placesindicated at 50, 50, there being only two gaps in the magnet ring. Oneof these gaps receives a deformable member 30 and the other receives aspring member 13. Of course, if some means other than a deformableinsert is used to obtain. compression of the spring member duringassembly, even the deformable member 30 of FIG. 30 may be eliminated andthe rotor made with only one gap between the magnets which gap is filledwith a spring member such as the member 13.

lclaim:

l. A method of making an assembly of magnets for a dynamoelectricmachine, said method comprising the steps of: forming an initialassembly of parts consisting of an annular part, an annular arrangementof generally arcuately shaped permanent magnets located within saidannular part in a generally end face to end face relationship to providepairs of adjacent end faces and with at least some of said pairs ofadjacent end faces being spaced from one another to provide gaps betweenadjacent magnets, and a plurality of inserts each received in arespective one of said gaps, said in serts including at least oneresilient biasing member and at least one deformable member, andthereafter deforming said deformable member in such a manner as toincrease its dimension circumferentially of said annular part so as tospread apart the magnets forming the gap in which it is received andcompressing said resilient member to cause said magnets to be thereaftertightly held against said annular part by the force exerted thereon bysaid resilient member.

2. The method defined in claim 1 wherein said deformable member is onewhich is deformable to increase its dimension circumferentially of saidannular part by a force applied thereto directed radially outwardly ofsaid annular part and wherein said step of deforming said deformablemember is accomplished by applying to said deformable member a forcedirected radially outwardly of said annular part.

3. The method defined in claim 1 further characterized by providing saidannular part in the form of an annular band, and providing a carrier ofmagnetic material having an axially extending rim with an internaldiameter at the outer edge of said rim approximately equal to theinternal diameter of said band, placing said annular arrangement ofmagnets over said rim with said band resting on said rim, and thereafterapplying forces simultaneously to all of said magnets to push themaxially out of said band and into said rim.

4. The method defined in claim 3 further characterized by furtherdeforming said deformable member after said magnets are received in saidrim to further compress said resilient member and to thereby cause saidmagnets to be more tightly held against said rim.

5. The method defined in claim 3 further characterized by making saidmagnets of an oriented ferrite material, and after said magnets arereceived in said rim magnetizing them to provide a plurality ofangularly spaced magnetic poles on the radially inner face of eachmagnet.

6. The method defined in claim 1 further characterized by providing saidannular part in the form of an annular band of magnetic material of sucha size as to provide a low reluctance flux path between magnetic polesformed on the radially outer faces of said magnets, and castingnon-magnetic material about said assembly to form a rotor with a rim ofsuch non-magnetic material having embedded therein said magnets, saidinserts and said annular band.

7. The method defined in claim 6 further characterized by making saidmagnets of an oriented ferrite material, and after said magnets areembedded in said rim magnetizing them to provide a plurality ofangularly spaced magnetic poles on the radially inner face of eachmagnet.

8. A method for making a field means for a dynamoelectric machine, saidmethod comprising the steps of:

providing a part having an annular inwardly facing surface, placing aplurality of generally arcuately shaped permanent magnets within saidannular surface in a generally end face to end face relationship toprovide pairs of adjacent end faces with at least some of said pairs ofadjacent end faces being spaced from one another to provide gaps betweenadjacent magnets, placing a resilient biasing member in one of saidgaps, placing a non-resiliently deformable member in another of saidgaps, and thereafter deforming said non-resiliently deformable member toincrease its dimension circumferentially of said annular surface so asto spread apart the magnets forming the gap in which it is received andto thereby compress said resilient member to cause said magnets and saidmembers to be held in a self-sustaining assembly with said part.

9. The method of making a field means for a dynamo-electric machine asdefined in claim 8 further characterized by providing said magnets in ade-magnetized condition prior to assembly with said part, andmagnetizing said magnets subsequent to their assembly with said part.

10. A method for making a field means for a dynamo-electric machine asdefined in claim 8 further characterized by providing saidnon-resiliently deformable member in the form of a tubular member havinga generally oval cross-section, said non resiliently deformable memberin said step of placing it in its gap being placed with its longitudinalaxis generally parallel to the axis of said annular surface and with themajor axis of its generally oval cross-section oriented generallyradially of said annular surface, and said step of deforming saidresiliently deformable member being accomplished by applying to it aforce directed radially outwardly of said annular surface so as todeform said deformable member toward a more circular shape.

11. A method for making a field means for a dynamo-electric machine asdefined in claim 8 further characterized by placing a nondeformablemember in another of said gaps before deforming said nonresilientlydeformable member.

1. A method of making an assembly of magnets for a dynamoelectricmachine, said method comprising the steps of: forming an initialassembly of parts consisting of an annular part, an annular arrangementof generally arcuately shaped permanent magnets located within saidannular part in a generally end face to end face relationship to providepairs of adjacent end faces and with at least some of said pairs ofadjacent end faces being spaced from one another to provide gaps betweenadjacent magnets, and a plurality of inserts each received in arespective one of said gaps, said inserts including at least oneresilient biasing member and at least one deformable member, andthereafter deforming said deformable member in such a manner as toincrease its dimension circumferentially of said annular part so as tospread apart the magnets forming the gap in which it is received andcompressing said resilient member to cause said magnets to be thereaftertightly held against said annular part by the force exerted thereon bysaid resilient member.
 2. The method defined in claim 1 wherein saiddeformable member is one which is deformable to increase its dimensioncircumferentially of said annular part by a force applied theretodirected radially outwardly of said annular part and wherein said stepof deforming said deformable member is accomplished by applying to saiddeformable member a force directed radially outwardly of said annularpart.
 3. The method defined in claim 1 further characterized byproviding said annular part in the form of an annular band, andproviding a carrier of magnetic material having an axially extending rimwith an internal diameter at the outer edge of said rim approximatelyequal to the internal diameter of said band, placing said annulararrangement of magnets over said rim with said band resting on said rim,and thereafter applying forces simultaneously to all of said magnets topush them axially out of said band and into said rim.
 4. The methoddefined in claim 3 further characterized by further deforming saiddeformable member after said magnets are received in said rim to furthercompress said resilient member and to thereby cause said magnets to bemore tightly held against said rim.
 5. The method defined in claim 3further characterized by making said magnets of an oriented ferritematerial, and after said magnets are received in said rim magnetizingthem to provide a plurality of angularly spaced magnetic poles on theradially inner face of each magnet.
 6. The method defined in claim 1further characterized by providing said annular part in the form of anannular band of magnetic material of such a size as to provide a lowreluctance flux path between magnetic poles formed on the radially outerfaces of said magnets, and casting non-magnetic material about saidassembly to form a rotor with a rim of such non-magnetic material havingembedded therein said magnets, said inserts and said annular band. 7.The method defined in claim 6 further characterized by making saidmagnets of an oriented ferrite material, and after said magnets areembedded in said rim magnetizing them to provide a plurality ofangularly spaced magnetic poles on the radially inner face of eachmagnet.
 8. A method for making a field means for a dynamo-electricmachine, said method comprising the steps of: providing a part having anannular inwardly facing surface, placing a plurality of generallyarcuately shaped permanent magnets within said annular surface in agenerally end face to end face relationship to provide pairs of adjacentend faces with at least some of said pairs of adjacent end faces beingspaced from one another to provide gaps between adjacent magnets,placing a resilient biasing member in one of said gaps, placing anon-resiliently deformable member in another of said gaps, andthereafter deforming said non-resiliently deformable member to increaseits dimension circumferentially of said annular surface so as to spreadapart the magnets forming the gap in which it is received and to therebycompress said resilient member to cause said magnets and said members tobe held in a self-sustaining assembly with said part.
 9. The method ofmaking a field means for a dynamo-electric machine as defined in claim 8further characterized by providing said magnets in a de-magnetizedcondition prior to assembly with said part, and magnetizing said magnetssubsequent to their assembly with said part.
 10. A method for making afield means for a dynamo-electric machine as defined in claim 8 furthercharacterized by providing said non-resiliently deformable member in theform of a tubular member having a generally oval cross-section, saidnon-resiliently deformable member in said step of placing it in its gapbeing placed with its longitudinal axis generally parallel to the axisof said annular surface and with the major axis of its generally ovalcross-section oriented generally radially of said annular surface, andsaid step of deforming said resiliently deformable member beingaccomplished by applying to it a force directed radially outwardly ofsaid annular surface so as to deform said deformable member toward amore circular shape.
 11. A method for making a field means for adynamo-electric machine as defined in claim 8 further characterized byplacing a non-deformable member in another of said gaps before deformingsaid non-resiliently deformable member.